Compact assistive reading device

ABSTRACT

A compact assistive reading device. A compact form factor is achieved through the use of an optical system with a pin hole aperture, which also obviates the needs for mirrors. One or more light sources are positioned outside the field of view of the optical system. A structure such as a prism film, patterned reflector or light pipe may be used to provide an illumination pattern that enhances the quality of images formed with the optical system. Additionally, processing components to recognize text, numbers or other information on an item placed in the imaging area of the optical system may be incorporated into a housing with the optical system. The housing contains features to facilitate easy insertion of an object into the imaging area and sensors to indicate when the object is properly positioned. The device may function as a currency reader.

BACKGROUND

1. Field of the Invention

The application relates generally to assistive devices for the visuallyimpaired and more specifically to compact assistive reading devices

2. Description of Related Art

Technology has been used to aid the visually impaired perform tasks thatmany sighted people take for granted. One such approach has been to usea camera to form images of documents or other items. A computer or otherdevice receives the output of the camera and enlarges it for display.Such magnification-based systems are useful only for partially-sightedusers.

Assistive devices have also been developed for users who cannot read orextract useful from a display, even if substantially magnified. Suchsystems have used audio output, such as speech to text converters, toconvert items containing text to a form that can be perceived by avisually impaired user. Such converters may be used to enable thevisually impaired to access information in books or other documentscontaining text.

One type of document is currency. In many countries, particularly theUnited States, all bills of currency are essentially the same size,regardless of denomination. As a result, without an assistive devicethat can read information printed on a bill, a visually impaired personwould be unable to determine the denomination of the bill. Accordingly,currency readers that can recognize and produce a non-visual outputindicating a denomination of a bill are known.

SUMMARY

An improved, compact assistive reading device is provided.

In one aspect, the invention relates to a compact apparatus forclose-range imaging of an object. The apparatus has a support structuredefining an imaging area. A surface with a pin-hole aperture is alsosupported by the support structure. An imaging array is supported by thesupport structure such that the surface is positioned with the pin-holeaperture disposed in an optical path between the imaging area and theimaging array. The imaging array is spaced from the imaging area by adistance of less than 25 mm, and at least 100 mm² of the imaging area isfocused on the imaging array through the pin-hole aperture. As anexample, the separation could be on the order of 15 mm.

In another aspect, the invention relates to a compact apparatus forclose-range imaging of an object. The apparatus has a housing havingdimensions of less than 100 mm in length, 20 mm in height and 50 mm inwidth. An imaging array and a planar imaging area are mechanicallycoupled to the housing. A planar surface having a pin hole aperture isalso mechanically coupled to the housing in an optical path between theimaging area and the imaging array.

In another aspect, the invention relates to a method of processing animage representing a bill of currency to detect a non-printed borderregion. The method may be performed with a processor and includesforming an array of values in a memory coupled to the processor. Thevalues in the array represent successive linear regions parallel to andoffset from a side of the image. Each value represents a number of edgepoints in a respective linear region. As part of the method a value inthe array that represents a linear region closest to the side that isabove a threshold is identified as a presumptive boundary between anon-printed and printed border region.

The identified non-printed border region may be omitted from the imagewhen processing is performed to identify a denomination of a bill ofcurrency depicted in the image. In some embodiments, this presumptiveboundary may be tested to ensure that pixels falling in the presumednon-printed border region can be reliably identified as representingnon-printed portions. When a reliable determination is not made, theborder region is assumed to be non-existent, which may increase theamount of processing required on the image, but does not degradeaccuracy.

The foregoing is a non-limiting summary of the invention, which isdefined by the attached claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, each identical or nearly identical component that isillustrated in various figures is represented by a like numeral. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1A is a sketch of a currency reader according to some embodimentsof the invention;

FIG. 1B is a sketch of the currency reader of FIG. 1A with a bill ofcurrency inserted for reading;

FIG. 2A is a schematic illustration of the currency reader of FIG. 1Bwith the bill inserted for reading and the housing shown in outlineform;

FIG. 2B is a side view of the currency reader illustrated in FIG. 2A;

FIG. 2C is a sketch of an optical position sensor used to detect theposition of the bill of currency in the currency reader of FIG. 2A;

FIG. 3 is a circuit schematic illustration of components of the currencyreader of FIG. 1A;

FIG. 4A is a top view, partially cut away, of the currency reader ofFIG. 1A;

FIG. 4B is a cross sectional view, partially cut away, along the lineB-B of FIG. 4A;

FIG. 5A is a cross section through the currency reader of FIG. 1A;

FIG. 5B is a different cross section through the currency reader of FIG.1A;

FIG. 6A is a schematic illustration of an optical path in a compactassisted reading device employing a patterned reflector according tosome embodiments of the invention;

FIG. 6B is a sketch of a patterned reflector that may be employed in anassistive reading device as illustrated in FIG. 6A;

FIG. 7 is a sketch illustrating compact dimensions in an optical systemof an exemplary embodiment of the currency reader of FIG. 1A;

FIG. 8 is a schematic illustration of a compact assistive reading deviceemploying a refractive element according to some embodiments of theinvention;

FIG. 9 is a schematic illustration of an alternative arrangement ofcomponents of an assistive reading device according to some embodimentsof the invention;

FIG. 10A is a sketch of an alternative embodiment of a compact assistivereading device incorporating pin hole optics according to someembodiments of the invention;

FIG. 10B is a cross sectional view of the assistive reading deviceillustrated in FIG. 10A;

FIG. 10C is a cross sectional illustration of the assistive readingdevice of FIG. 10B in an alternative operating state;

FIG. 11 is a schematic illustration of components in a compact assistivereading device employing a solid state optical chamber and light pipeaccording to some alternative embodiments of the invention;

FIG. 12A is a sketch of a currency reader according to some embodimentsof the invention;

FIG. 12B is a sketch of the currency reader of FIG. 12A with a bill ofcurrency inserted for reading;

FIG. 13A is a sketch of a portable electronic device (such as a cellphone) with a built in camera that may be fitted with an optical systemto form an assistive reading device;

FIG. 13B is a sketch of the cell phone of FIG. 13A with opticalcomponents attached to form an assistive reading device according tosome embodiments of the invention;

FIG. 13C is a cross section of the assistive reading device of FIG. 13Bthrough the line C-C of FIG. 13B;

FIG. 13D is a schematic illustration of a focusing mechanism that may beincorporated into the optical component illustrated in FIG. 13B;

FIG. 13E schematically illustrates the focusing mechanism of FIG. 13Dfrom an alternative perspective;

FIG. 14 is a flow chart of an exemplary method of operation of anassistive reading device according to some embodiments of the invention;

FIG. 15 is a flow chart of an exemplary process for identifying adenomination of a bill in an assistive reading device according to someembodiments of the invention;

FIG. 16 is a flow chart of a method of processing an image to identify aprinted area of a bill of currency according to some embodiments of theinvention; and

FIG. 17 is a flow chart of a method of detecting a border on a bill ofcurrency that may be used as part of identifying a print area accordingto the method of FIG. 16.

DETAILED DESCRIPTION

Applicant has recognized and appreciated that available assistivereading devices can be improved by making such devices compact and easyfor visually impaired users to operate. Applicant has furtherappreciated that an assistive reading device can be made compact throughthe use of an optical imaging system with a pin hole aperture. Such anoptical system may be coupled to a processing system within a compacthousing formed with simple input and output devices that make the deviceeasy to operate.

In embodiments in which the assistive reading device reads currency, thehousing may be shaped to aid a visually impaired person position aportion of a bill in an imaging area. With a bill properly positioned inthe imaging area, the currency reader may acquire and process an imageof at least a portion of the bill from which the denomination of thebill can be recognized.

The device may have one or more output devices, such as a speaker ormechanical vibrator, to allow a recognized denomination of a bill to bepresented in a audible, tactile or other non-visual format. An outputdevice may also be used to communicate device status, such as toindicate that the device is on or off or that a bill has been correctlypositioned in the device for reading.

The device also may have an input device or devices that can be simplyoperated to allow the user to input commands to control the device, suchas commands to power on the device or to provide or repeat an outputindicating a denomination of a bill. The input device may also allow auser to provide commands that control the form of the output, such as toturn on or off specific output devices so as to switch between outputmodes. Other commands may change the volume or intensity of an outputindicator, regardless of the output mode used.

FIG. 1 illustrates as an example of a compact assistive reading device acurrency reader 100. Currency reader 100 has a compact form factor,providing an overall size suitable for carrying the device in a user'spocket. In some embodiments, the currency reader will have a width, W,of a 100 millimeters or less, a length, L, of 50 millimeters or less anda height, H, of 20 millimeters or less. In the embodiment illustrated,currency reader 100 has dimensions of approximately 74 millimeters by 40millimeters by 18 millimeters.

Housing 110 encloses and acts as a support structure for components,such as an optical imaging system and processing components.Additionally, housing 110 may support one or more input devices or moreoutput devices.

Housing 110 may be constructed of any suitable material or materials.These materials may be formed into one or more members, suitably shapedto form housing 110 using any suitable construction techniques. In theembodiment illustrated, some or all of the components of housing 110 maybe molded from plastic using known molding techniques.

The members of housing 110 may be provided with features that facilitatea visually impaired user firmly grasping currency reader 100 and/orappropriately orienting currency reader 100 for use. For example,textured gripping surface 112 may be formed with a plurality of bumps orprojections that can be easily felt by a user. Accordingly, texturedgripping surface 112 provides a mechanism for a visually impaired userto identify the top surface of currency reader 100. Similarly texturedgripping corners, of which textured gripping corner 114A is visible inFIG. 1A and textured gripping corner 114B visible in FIG. 1B, may alsobe included. As can be seen in FIG. 1A, textured gripping corner 114Aincludes multiple bumps or projections that can be felt by a visuallyimpaired user, allowing the user to identify the rear corners ofcurrency reader 100 by touch.

Textured surfaces, such as textured gripping surface 112 and texturedgripping corners 114A and 114B may be formed of the same material usedin forming other members of housing 110. In some embodiments, thetextured surfaces may be integral with other portions of the housing.However, in other embodiments, the textured surfaces may be formed of orcoated with materials that enhance gripping of currency reader 100. Forexample, gripping surfaces may be formed with rubberized plastic or maybe coated with rubber, vinyl or other relatively soft material thatfacilitates gripping. Though, the materials used are not critical in theinvention and any suitable materials may be used and formed intotextured surfaces in any suitable way.

Housing 110 may also contain other features. For example, FIG. 1Aillustrates a hole 118 through a corner of housing 110. Hole 118 may besized for attaching currency reader 100 to another member, such as akeychain or a lanyard. By attaching currency reader 100 to such amember, a user may readily carry or locate currency reader 100.

In the embodiment illustrated, housing 110 is formed from at least twomembers, an upper member 110U and a lower member 110L. These members maybe held together in any suitable fashion. For example, upper housingmember 110U and lower housing member 110L may be held together withscrews, adhesive and/or snap fit features. Forming housing 110 ofmultiple members allows currency reader 100 to be assembled by placingan optical imaging system and processing components inside housing 110and then fixing upper housing member 110U to lower housing member 100L.However, any suitable construction techniques may be used.

In the embodiment illustrated, housing 110 is formed from at least athird member. In the example illustrated in FIG. 1A, housing 110 alsoincludes battery compartment cover 116. Battery compartment cover 116may be removably connected to other components of housing 110, therebyallowing a battery to be installed within currency reader 100 after itis manufactured to provide power for operation of the device. Though,any suitable mechanism for supplying power may be used.

In addition to enclosing the optical imaging system and processingcomponents, housing 110 is adapted for receiving a bill of currency andto support user input devices. In the embodiment illustrated, currencyreader 100 includes user input devices that are easy for a visuallyimpaired user to correctly actuate. In the embodiment illustrated, theuser input devices consist of two buttons, 120A and 120B (FIG. 4A). Inthe embodiment of FIG. 1A, buttons 120A and 120B are positioned inopposing side surfaces of housing 110. Also as illustrated in FIG. 1A,each of the buttons has a textured surface, allowing a visually impaireduser to locate the button tactilely. In the embodiment illustrated, eachbutton 120A and 120B performs the same function when pressed, such thata user need not differentiate between button 120A and 120B to operatecurrency reader 100. Rather, a user may input different commands tocurrency reader 100 based on the number of buttons pressed. In this way,a user may input multiple commands to control currency reader 100 toperform multiple functions through a relatively simple user interface.

As a specific example, depressing either button 120A or 120B may beinterpreted by processing components within currency reader 100 as acommand to initiate a process of determining a denomination of a billinserted into currency reader 100. Pressing both buttons 120A and 120Bsimultaneously may be interpreted by the processing components as acommand to turn on the device or to change a level of the output. Foraudible outputs, depressing both buttons may alter the volume of theoutput. For example, currency reader 100 may be configured to operateaccording to one of a set of possible volume levels. Each time buttons120A and 120B are pressed together, the device may switch to the nextlowest volume level. The volume levels may be arranged cyclically suchthat when both buttons 120A and 120B are depressed while the currencyreader 100 is already in the lowest volume level, currency reader 100may respond by transitioning to the highest volume level.

In embodiments in which currency reader 100 supports multiple outputmodes, the simple push-button interface may be used both to changeoutput levels and output modes. As an example, the output levels mayinclude a mix of volume levels and intensity levels for a mechanicalvibrator output device. In such embodiments, depressing both buttons120A and 120B when the currency reader 100 is already operating in thelowest volume setting may result in the device switching to an operatingmode in which outputs are represented by vibration pulses of the device.As with volume output levels, multiple vibration output levels couldalso be defined. In such an embodiment, depressing buttons 120A and 120Bwhile the currency reader 100 is already in a vibratory output mode mayresult in a decrease in the intensity of the vibration pulses.

Regardless of the manner in which a user inputs a command indicatingthat the denomination of a bill is to be read, to use the device, a userinserts a bill of currency into currency reader 100. With the bill inthe device, the user may input a command, such as by activating one ofbuttons 120A and 120B, to specify that currency reader 100 should readthe denomination of the bill and produce a non-visual output indicatingthat denomination.

For currency reader 100 to read the denomination of a bill, a feature ofthe bill indicative of its denomination is positioned within currencyreader 100 in an imaging area of an optical imaging system. Tofacilitate such positioning of a bill, housing 110 is formed with a slot130 sized to receive a bill of currency and guide at least a portion ofthe bill into an imaging area.

As illustrated in FIG. 1A, slot 130 may be shaped to facilitateinsertion of a bill of currency by a visually impaired user. As shown,slot 130 has a protruding floor 132, forming a shelf on which a user mayrest a forward edge of a bill of currency. With the bill of currencyresting on floor 132, a user may push it towards the rear of housing110, forcing the front edge of the bill of currency under upper edge136. Once the forward edge of the bill of currency is under upper edge136, the forward edge is fully enclosed within slot 130 and, as the userpresses the bill further towards the rear edge of housing 110, the billwill be guided into position in the imaging area of the optical imagingsystem within housing 110. FIG. 1B illustrates a bill of currency 150inserted into slot 130.

To further facilitate insertion of a bill of currency, side walls 134Aand 134B in the areas adjacent floor 132 are tapered. As can be seen inFIG. 1A, the tapering of sidewalls 134A and 134B creates a wider openingto slot 130 at the forward edge of floor 132 than adjacent to upper edge136. This tapering facilitates placement of the forward edge of a billof currency against floor 132 while constraining the position of thebill of currency when it is fully inserted into slot 130. Though, itshould be appreciated that, while the structure illustrated of slot 130facilitates use of currency reader 100 by a visually impaired user, anysuitable mechanism for receiving a bill of currency may be used.

In some embodiments, insertion of a bill of currency into an assistivereading device may cause the device to power on. Such an embodiment maybe implemented, for example, by incorporating a sensor adjacent theopening of slot 130. Such a sensor may be implemented as a switch,capacitive sensor, magnetic sensor or other suitable type of sensor.When the sensor detects the presence of a bill in slot 130, it may powerup the device, preparing the device to recognize a denomination of abill without requiring a user to expressly power on the device. Though,in some embodiments, the device does not attempt to recognize that abill is improperly inserted into the device, which may be ascertainedfrom one or more position sensors within the device. Audible tones maybe used to provide feedback to a user by indicating when a bill isdetected in slot 130 and whether the bill is properly positioned forimaging a predetermined area of the bill. In embodiments in which asensor is included to detect the presence of a bill, a recognitionprocess may begin automatically once the bill is determined to beproperly positioned.

FIG. 2A schematically illustrates bill 150 positioned within slot 130 inhousing 110. As can be seen in FIG. 2A, each corner of bill 150, such ascorners 252A and 252B, contains a numerical designation of thedenomination of bill 150. Though not shown in FIG. 2A, within housing110 an optical imaging system is positioned relative to slot 130 suchthat, when bill 150 is fully inserted into slot 130 a corner of bill 150will be adjacent an imaging area of the optical imaging system. In thisway, a corner of bill 150 including a numerical designation of thedenomination of the bill will be in the imaging area of the opticalimaging system when the bill 150 is fully inserted in slot 130. Though,it should be appreciated that the portion of the bill in the imagingarea need not include a numerical designation. Any portion of the billthat has recognizable characteristics may be placed in the imaging areaand the denomination of the bill may be determined based on matchingthat portion of the bill to a template associated with a specific billdenomination or otherwise determining that the characteristics arepresent in the imaging area.

In the embodiment illustrated, currency reader 100 includes one or moreposition sensors that can detect the position of bill 150 and ascertainwhen it is fully inserted into slot 130. The outputs of the positionsensors may be used in any suitable way. For example, the positionsensors may be coupled to processing components within currency reader100 and used to trigger a process of reading the denomination of bill150. The processing components, for example, may capture an image of theimaging area in response to an indication from the position sensors thatbill 150 is fully inserted into slot 130 (FIG. 1). Alternatively,processing components may output an indication to a user that bill 150has been properly positioned within slot 130 in response to the outputsof the position sensors. Such an output indication may prompt a user toactivate input devices for currency reader 100 that cause the processingcomponents to capture an image and identify a denomination of bill 150.As a further alternative, the outputs of the position sensors may beused to generate an output that serves as a warning to a user that thebill is not properly positioned in the housing when the user inputs acommand to read the denomination of the bill. Thus, the specific mannerin which the outputs of position sensors are used as part of a processof reading a denomination of bill 150 is not critical to the inventionand they may be used in any suitable way.

In the embodiment illustrated in FIG. 2A, three position sensors,position sensors 210A, 210B and 210C, are included within currencyreader 100. Each position sensor is mounted within housing 110 such thatit will be adjacent an edge of bill 150 when bill 150 is correctlypositioned within slot 130 (FIG. 1A).

As illustrated, position sensor 210A is mounted within housing 110 in alocation that corresponds with a side edge of bill 150 when the bill iscorrectly inserted into slot 130. Position sensors 210B and 210C aremounted within housing 110 such that they will detect the forward edgeof bill 150 when the bill is properly inserted into slot 130. With thismounting of position sensors 210A, 210B and 210C, when all three sensorsoutput an indication of the presence of bill 150, processing componentsin currency reader 100 can determine that bill 150 is properlypositioned for reading.

In the embodiment illustrated in FIGS. 2A and 2B, position sensors 210Aand 210B and 210C may be optical position sensors. FIG. 2C illustrates apossible instruction of such optical position sensors. Each positionsensor may include a light source 212 and a light sensor 214. As anexample, light source 212 may be a light emitting diode (LED) and lightsensor 214 may be a photo transistor. However, any suitable componentsmay be used as a light source and/or a light sensor, including, as oneexample, an optical fiber guide that directs light to the primaryimaging array rather than dedicated light sensors.

As shown, light source 212 may be directed at a smooth surface ofhousing 110. Light sensor 214 may be directed generally at the samelocation of housing 110. When no bill is present, light from lightsource 212 reflects from the smooth surface of housing 100 and isdetected by light sensor 214. If a bill 150 is present in slot 130, lesslight will reflect from the bill than reflects from the surface ofhousing 110. Accordingly, the amount of light measured by sensor 214decreases when a bill is inserted between sensor 210 and housing 110.Processing components coupled to position sensor 210 may, therefore,detect the presence of a bill positioned within slot 130 based on thelevel of light sensed by light sensor 214. Though, any suitable positionsensors may be used, including, for example, electromechanical switches,capacitive sensors or magnetic sensors.

Regardless of the type of position sensors used, the position sensorsmay be arranged within the housing to detect when the bill is inposition for reading the denomination of the bill. In the exampleillustrated, when bill 150 is properly positioned, corner 252A ispositioned in an imaging area 230 of an optical system within housing110. FIG. 2B shows this positioning.

FIG. 2B illustrates housing 110 from the prospective of line B-B in FIG.2A. In FIG. 2B, housing 110 is shown in outline form to reveal thepositioning of some of the components inside housing 110.

FIG. 2B illustrates that the floor of slot 130 under upper edge 136contains a transparent window 232. In the embodiment illustrated,transparent window 232 is formed of a transparent member, such as aplastic or glass sheet. However, any suitable material may be used toform window 232, and in some embodiments, a transparent window may beformed as an opening within the material used to form housing 110without any member inserted in the opening.

Regardless of the material used to form window 232, window 232 providesan imaging area 230 for an optical system within housing 110. In theembodiment illustrated, window 232 is positioned such that corner 252Aof bill 150 is positioned in imaging area 230 when bill 150 is properlyaligned within slot 130.

In the embodiment illustrated, a compact optical system is formed usinga pin hole aperture. Such an optical system may include an apertureplate 220 containing a pin hole aperture 224. The pin hole aperture 224may be between imaging area 230 and an imaging array 222. In this way,an image of an object, such as the corner of a bill 150, within imagingarea 230 may be focused on an imaging array 222. Imaging array 222 maythen capture an image of the object for further processing.

Imaging array 222 may be an imaging array as is known in the art. Forexample, imaging array 222 may be an array of charge coupled devicesthat can be connected to other processing components within currencyreader 100. However, a CMOS sensor array or any other suitable form ofimaging array may be used.

Turning to FIG. 3, a schematic illustration of components of currencyreader 100 is provided. In the embodiment illustrated, processing isprovided in a processor, such as microcontroller 310. As illustrated,microcontroller 310 includes embedded memory 312 in which a program maybe stored. The program may control microcontroller 310 and, hence, othercomponents of currency reader 100, to perform operations that result indetermining denomination of a bill of currency.

As shown, microcontroller 310 is coupled to position sensors 210A, 210Band 210C. As a result of these connections, a program stored in memory312 may include conditional operations that depend on whether positionsensors 210A, 210B and 210C produce outputs indicating that a bill isproperly positioned within slot 130. This conditional operation mayinclude, for example, outputting a warning to a user that a bill is notproperly positioned when the user inputs a command to read thedenomination of a bill. Alternatively, these conditional operations mayinclude triggering a process that captures an image of at least aportion of a bill inserted into slot 130 when the outputs of positionsensors 210A, 210B and 210C indicate that the bill is properlypositioned.

The program for microcontroller 310 may also include conditionaloperations that are based on user inputs. As shown in FIG. 3, switches320A and 320B are also coupled to microcontroller 310. Switches 320A and320B are positioned behind buttons 120A and 120B, respectively.Accordingly, when a button 120A or 120B is depressed by a user, itscorresponding switch will momentarily change state, producing a signalthat can be detected by microcontroller 310. In this way,microcontroller 310 may be programmed to respond to user inputs throughbuttons 120A and 120B.

FIG. 3 also indicates that imaging unit 330 is coupled tomicrocontroller 310. Image unit 330 may include imaging array 222 onwhich an image of corner 252A is focused by pin hole aperture 224 (FIG.2B). The connections between microcontroller 310 and image unit 330 mayinclude both control and data paths. Using these paths, whenmicrocontroller 310 determines, based on the signals received fromswitches 320A or 320B and signals from position detectors 210A, 210B and210C that the denomination of a bill is to be read, microcontroller 310may generate outputs acting as control inputs to image unit 330. Thesecontrol inputs may cause imaging array 224 to capture an image andoutput data representing the pixels of that image to microcontroller310.

Microcontroller 310 may perform one or more algorithms on that imagedata to determine the denomination of the bill inserted into slot 130(FIG. 1A). Such processing may be performed in any suitable way. In someembodiments, a denomination may be detected by performing a crosscorrelation between groups of pixels in the captured image and prestoredset of templates representing unique patterns printed on currency ofspecific denominations. In some instances, the unique patterns mayinclude all or a portion of a numeral representing a denomination of thebill. Though, it is not a requirement that the pattern be a numericalindicator. A template in the set with a high cross correlation to thecaptured image may be regarded as matching the denomination of the bill.In this way, the denomination associated with the matching template maybe output to a user as the denomination of the bill.

Regardless of the specific mechanism used to determine the denomination,the determined denomination may be output to the user through any one ormore suitable output devices. In the embodiment shown in FIG. 3, twooutput devices are illustrated, speaker 340 and mechanical vibrator 350.Here, speaker 340 is used to output an audible indication of therecognized denomination. Vibrator 350 is used to cause currency reader100 to vibrate in pulses, with the pattern of pulses signaling thedetermined denomination. For example, one pulse may signal a one dollarbill; two pulses may signal a 2 dollar bill; three pulses may signal afive dollar bill; etc. However, any suitable pattern of pulses may beused.

To generate the vibration pulses, currency reader 100 may include adriver 352 that powers vibrator 350 in response to a control signalgenerated by microcontroller 310. Driver 352 and vibrator 350 may becomponents as known in the art. Though, any suitable components may beused.

The audible output produced by speaker 340 may likewise be in the formof a series of pulses—though audible. Speaker 340 may output a series ofblips or other sounds representing the detected denomination of a bill.Though, an audible output may be encoded in other ways to signify thedenomination of a bill. For example, tones of different frequency maysignal different denominations. In other embodiments, speaker 340 mayoutput an indication of the detected denomination using synthesizedspeech. In such an embodiment, microcontroller 310 may be programmed tooutput a signal that, when applied to speaker 340, produces speech.

In the embodiment illustrated, microcontroller 310 outputs a stream ofdigital bits using pulse code modulation. That stream of bits is appliedto digital-to-analog converter 342. The output of digital-to-analogconverter 342 is filtered in audio filter 344 and applied to an audioamplifier 346. As shown, audio amplifier 346 drives speaker 340. In thisway, by appropriately programming microcontroller 310 to generate adigital stream in a suitable pattern, the format of the audio output maybe controlled.

Microcontroller 310 may also be programmed to perform other operationsassociated with reading denomination of a bill. For example, currencyreader 100 may include a source of illumination 332 directed at imagingarea 230 (FIG. 2B). To conserve power, illumination source 332 may beturned on only when imaging array 222 is to capture an image.Accordingly, illumination source 332 may be coupled to microcontroller310 through a driver 334. Driver 334 may be configured to only supplypower to illumination source 332 when microcontroller 310 asserts acontrol line indicating that an image is to be captured.

Other components of currency reader 100 are also illustrated in FIG. 3.Power for operation of the electronic components may be supplied by abattery 360. Appropriate power levels may be supplied through a voltageconverter 362. As shown, voltage converter 362 provides power frombattery 360 to microcontroller 310, switches 320A and 320B, imagingarray 330, driver 334, digital-to-analog converter 342, amplifier 346and driver 352.

FIG. 3 also illustrates a download and test port 370 may be included.Such a port may allow a program to be downloaded into memory 312. Such aport may also allow test signals to be coupled to and frommicrocontroller 310 to test operation of currency reader 100.

The circuitry illustrated in FIG. 3 may be implemented usingcommercially-available electronic components. However, the circuitry maybe implemented in an Application Specific Integrated Circuit (ASIC) or aprogrammable device, such as a gate array. Accordingly, any suitablecomponents may be used.

In some embodiments, the components may be packaged to facilitatecompact construction of currency reader 100. As an example, multiplecomponents illustrated in FIG. 3 may be fabricated on a single printedcircuit board. For example, microcontroller 310, driver 334,digital-to-analog converter 342, audio filter 344, amplifier 346 andvoltage converter 362 may be attached to and interconnected through theprinted circuit board. Other components may be mounted to otherlocations within housing 110 and interconnected to the printed circuitboard using wires, flex circuits or other suitable means.

FIG. 4A shows a possible layout of such components to achieve a compactarrangement. In FIG. 4A, housing 110 is shown in outline form. Printedcircuit board 410 is shown mounted in one corner of housing 110. Asshown, speaker 340 is mounted to a floor of housing 110. As shown,switches 320A and 320B are positioned adjacent buttons 120A and 120B. Apossible position for battery 360 is also illustrated.

As can be seen, imaging unit 330 is positioned to align with window 232.Illumination source 332 is positioned to illuminate window 232. Thoughany suitable positioning may be used, in the embodiment illustrated, theillumination source is placed outside the field of view of the imagingunit. The inventor has recognized and appreciated that this positioninglimits reflection of the light source from the window, reducinginterference with the image. By reducing interference, the recognitiontask may be simpler and more accurate. In the embodiment illustrated inFIG. 4A, illumination source 334 is implemented as two light emittingdiodes, LED 434A and 434B.

FIG. 4B shows the structure of FIG. 4A from the perspective of line B-Bin FIG. 4A. As can be seen in FIG. 4B, printed circuit board 410 ismounted, such as through mounting members 430A and 430B, to a topsurface of currency reader 100. Speaker 340 is mounted to a lowersurface. This mounting leaves a space through which light from LEDs 434Aand 434B may pass to reach window 232.

FIG. 5A provides an alternative view of components inside housing 110 ofcurrency reader 100. FIG. 5A shows a cross section through currencyreader 100. In the embodiment illustrated in FIG. 5A, window 232 is setback from the surface of housing 110 defining slot 130, creating arecess 530. Recess 530 prevents a bill 150 from sliding across an uppersurface of window 232 when inserted in slot 130. Accordingly, recess 530may improve the accuracy of currency reader 100 by preventing scratchingof window 232 by contaminants on bill 150. By avoiding scratches orother contamination of window 232, a more accurate image of bill 150 maybe captured.

FIG. 5A also illustrates a further feature that may be incorporated toimprove the accuracy of currency reader 100. As illustrated, a patternedreflector is included adjacent window 232. Patterned reflector 520 ispositioned to reflect light from LEDs 434A and 434B towards window 232.Patterned reflector 520 is positioned to compensate for unevenillumination across window 232 caused by LEDs 434A and 434B beingpositioned to illuminate window 232 from an oblique angle.

As shown, LEDs 434A and 434B will provide greater direct illumination atthe side of window 232 closest to LEDs 434A and 434B. Patternedreflector 520 is positioned to reflect light to preferentiallyilluminate the side of window 232 that is farthest from LEDs 434A and434B. In this way, the combination of illumination directly from LEDs434A and 434B and illumination reflected from patterned reflector 520may be relatively constant across window 232.

FIG. 5B shows a cross section of currency reader 100 similar to thatshown in FIG. 5A. The cross section of FIG. 5B differs from that in FIG.5A and that it is taken through a different section of currency reader100.

FIG. 6A illustrates operation of the patterned reflector 520. As shown,LEDs 434A and 434B are positioned at an oblique angle relative to window232 behind which an object, such as bill 150 is positioned. As can beseen, the rays of light from LEDs 434A and 434B that illuminatedifferent portions of window 232 can have different properties, tendingto cause variations in illumination across window 232. For example, ray660A illuminating the edge of window 232 closest the LEDs 434A and 434Btravels a shorter distance and strikes window 232 at a less obliqueangle than ray 660B that illuminates the farther edge of window 232. Insuch a configuration, ray 660B may provide less intense illuminationthan ray 660A.

To compensate for differences in direct illumination, patternedreflector 620 is positioned such that a portion of the light emitted byLEDs 434A and 434B strikes patterned reflector 620 and is reflected,such as in ray 662 towards window 232. The combination of illuminationdirectly from LEDs 434A and 434B and that reflected from patternedreflector 620 combines to provide a more uniform illumination of window232 than could be provided by light from LEDs 434A and 434B alone.

As shown, the patterned reflector 620 can compensate, at leastpartially, for variations in illumination across window 232 based ondistance from LEDs 434A and 434B. In addition to variations inillumination associated with distance, variation in illumination mayalso occur across window 232 as a result of angular direction. Forexample, FIG. 4A shows beams from LEDs 434A and 434B illuminating window232. Points 668A and 668B are both at substantially the same distancefrom the source of illumination. However, point 668A is closer to thebeam center than point 668B. Accordingly, illumination at point 668A maybe more intense than at point 668B.

To compensate for this difference in intensity based on angulardirection, patterned reflector 620 may have a pattern that reflectsdifferent amounts of light, depending on the angle relative to the beamsemitted by LEDs 434A and 434B. FIG. 6B illustrates a possible pattern.FIG. 6B shows a front view of patterned reflector 620, which is incontrast to the side view in FIG. 6A. As shown, patterned reflector 620has different reflectivity at different locations on its surface. Thispattern of reflectivity may be selected to provide more reflectivity atbeam angles where less illumination is received and less reflectivity atbeam angles where greater illumination is received. Accordingly, FIG. 6Billustrates that patterned reflector 620 has a central portion 670 thatis less reflective than side portions 672 and 674. As shown, the amountof reflectivity may vary continuously across the surface of patternedreflector 620.

Though not expressly illustrated in FIG. 6B, other variations may beincorporated into the reflectivity pattern of patterned reflector 620 tocompensate for other variations in the intensity of the illumination.For example, the reflectivity of patterned reflector 620 may vary acrossthe surface of patterned reflector 620 from bottom 676 to top 678.

Enabling relatively uniform illumination from an oblique angle asillustrated in FIG. 6A allows for a compact design of an assistivereading device, particularly in combination with an optical imagingsystem incorporating a pinhole lens. As illustrated, an optical imagingsystem using a pinhole lens can provide a relatively large field of viewthat spans an angle, A. As a result, window 232 maybe in the field ofview of the imaging system, even though imaging array 222 is spaced fromwindow 232 by a distance D₁, which can be relatively small. Distance D₁may be less than the height of currency reader 100, and in someembodiments may be a substantial factor in defining the height of thedevice.

FIG. 7 provides examples of dimensions of an optical imaging systememploying a pinhole lens that may lead to a compact assistive readingdevice. In the example of FIG. 7, imaging area 230 is on the order of 1in². As a specific example, FIG. 7 illustrates that imaging area 230 is0.94 in. An imaging array 222 is on the order of 0.1 in². In a specificexample of FIG. 7, the imaging array 222 is 0.09 in². As shown, imagingarray 222 is separated from aperture plate 220 by a distance of 0.04 in.This separation provides a field of view in excess of 75 degrees. In theexample of FIG. 7, the field of view is 83.7 degrees. With this field ofview, an image of items in imaging area 230 may be focused on imagingarray 222 with a separation between imaging area 230 and imaging array222 on the order of one half in. In the example of FIG. 7, theseparation D₁ 0.56 in.

Though the specific dimensions of FIG. 7 are illustrative rather thanlimiting of the invention, they demonstrate a suitable implementation ofa compact assistive device.

FIG. 8 illustrates an alternative embodiment of imaging components in acompact assistive reading device. The embodiment of FIG. 8 includes apinhole optical imaging system, which may be formed from an apertureplate 220 with a pinhole 224 focusing images of objects in an imagingarea onto an imaging array 222. As in the embodiment of FIG. 6A, theimaging area 230 is illuminated from an oblique angle. In the example ofFIG. 8, imaging area 230 is illuminated by a light emitting diode (LED)834. Though, any suitable illumination source may be used.

As shown, LED 834 directs a beam of light generally at the center ofimaging area 230. To increase the uniformity of illumination crossimaging area 230, a refractive element may be positioned in the path ofthe beam of light. A refractive element can redirect the beam of lightfrom LED 834 to impinge on window 232 in a substantially perpendiculardirection. With this incident angle, more of the light from LED 834 isdirected into imaging area 230, increasing both the intensity anduniformity of the illumination across imaging area 230. In theembodiment illustrated, the refractive element is a prism film 832applied to a lower a surface of window 232. Prism film is known in theart and suitable prism film may be commercial procured. However, anysuitable refractive element may be used.

FIG. 8 does not illustrate a reflector perpendicular to window 232, suchas pattern reflector 620 (FIG. 6A). However, a reflector may beincorporated into the design of FIG. 8 and that reflector may bepatterned as illustrated in FIG. 6B or with any other suitable patternto provide uniform illumination across imaging area 230.

FIG. 9 illustrates an alternative embodiment of an imaging system thatmay be employed in a compact assistive device. In the embodiments ofFIG. 6A and FIG. 8, imaging array 222 is oriented parallel to window 232defining imaging area 230. FIG. 9 illustrates an alternative embodimentin which imaging array 222 is also positioned at an oblique anglerelative to imaging area 230.

Though not a requirement of the invention, in the embodiment illustratedin FIG. 9, aperture plate 220 is mounted perpendicular to window 232defining imaging area 230. As shown, aperture plate 220 is positioned tothe same side of imaging area 230 as LED 834. However, aperture plate220 is positioned out of the path of a beam emanating from LED 834.

Imaging array 222 is positioned behind aperture plate 220 such thatpinhole 224 in aperture plate 220 is in the optical path of lightreflected from imaging area 230 that is focused by pinhole aperture 224.In the embodiment illustrated, imaging array 222 is mounted at an angleB. Mounting imaging array 222 at an angle can compensate for distortioncaused by having the imaging array at an oblique angle.

For example, as illustrated in FIG. 9, a ray, such as ray 960A,reflected from a near portion of imaging area 230, such as region 970A,travels a relatively short distance to imaging array 222, which wouldtend to cause items in region 970A to appear larger than items in region970B that are farther from imaging array 222. However, as can be seenfrom the path of 960B, representing a reflection from an object inregion 970B, the tilt of imaging array 222 ensures that ray 960B has alonger path from pinhole 224 to imaging array 222 than does ray 960A. Alonger path from the pinhole 224 to the imaging array 222 tends tointroduce magnification into the image. Accordingly, the tilt angle B ofimaging array 222 may be selected such that demagnification associatedwith objects in region 970B in comparison to objects in region in 970Ais offset by the apparent magnification of objects imaged at region 972Bof imaging array 222 relative to those objects imaged in region 972A. Inthis way, a relatively uniform magnification across imaging area 230 maybe provided, which can facilitate accurate identification of objects inimaging area 230, even though the optical system is relatively compact.

In the embodiment of FIG. 9, placing imaging array 222 to the side,rather than parallel and facing window 232, may allow a decrease in theheight of an assistive reading device. For example, FIG. 9 illustratesthat the distance in the space dimension required to accommodate both anillumination source and imaging system is D₂. In some embodiments, thedistance D₂ may be less than the distance D₁ (FIG. 8) when the imagingarray is parallel to window 232.

Other than the positioning of aperture plate 220 and imaging array 222,the components used in forming the assistive reading device illustratedin FIG. 9 may be the same as described above in connection with theembodiments of FIG. 6A or FIG. 8. Though, any suitable components may beused.

In the foregoing examples, principles for making a compact assistivereading device have been illustrated embodied in a currency reader.Though, the invention is not so limited. The invention may be employedfor reading numbers or letters or recognizing other symbols on paper orother planar objects that may be placed in an imaging area. FIG. 10Aillustrates a planar object 1050 placed on a housing 1010 with a window232. Window 232 exposes a portion of object 1050, allowing an image ofthe portion to be focused by pinhole 224 onto imaging array 222.Processing of the image captured on imaging array 222 may be performedin components as described above in connection with FIG. 3. Toaccommodate processing of objects other than currency, the programsstored in memory 312 may, rather than recognizing indications ofdenominations of bills of currency, may be adapted to recognize text,numbers or other symbols that may appear on object 1050. Though anysuitable processing components may be used.

FIG. 10B is a cross-sectional view of the embodiment of FIG. 10A. In theembodiment of FIG. 10A, portions of housing 1010 are not illustrated forclarity. In the embodiment of FIG. 10B, housing 1010 is illustrated ashaving members that position and support aperture plate 220 and imagingarray 222 for appropriate imaging of the imaging area created by window232. In the embodiment illustrated, housing 1010, in addition to havinga surface in which window 232 is formed, contains members 1012 thatdefine the position of aperture plate 220. Members 1012 may also definethe position of a substrate 1014 that positions and supports imagingarray 222. In the embodiment illustrated, the members of housing 1010that position and support other components of the assistive readingdevice may be integrally formed with the member in which window 232 isformed. Such an embodiment may be implemented by forming the supportmembers of housing 1010 in the same molding operation as the outersurfaces of the housing. However, it is not a requirement that thesupport members be integrally formed, and any suitable constructiontechniques may be used.

FIG. 10C illustrates that the techniques for forming a compact assistivereading device are not limited to use in constructing assistive devicesthat read text, numbers or other symbols on flat objects, such as paperor bills of currency. FIG. 10C illustrates that three-dimensionalobjects, such as objects 1060A and 1060B, may be positioned in animaging area adjacent to window 232 such that imaging array 222 maycapture an image of those objects. Objects 1060A and 1060B may beobjects such as pills or hearing aide batteries that contain text,numbers or symbols. Alternatively or additionally, the objects 1060A and1060B may be shaped or have features that a visually impaired person maynot be able to perceive without assistance. Though, an assistive devicemay be configured to recognize any suitable types of objects, includingobjects from mainstream use, other than objects a visually impairedperson may seek to recognize. The images captured with imaging array 222in the embodiment of FIG. 10C may be processed using components asillustrated in FIG. 3 or any other suitable components. Though, theprogram stored for micro-controller 310 maybe adapted to recognizecharacteristics of objects 1060A and 1060B. Those characteristics mayinclude the shape, size, presence or absence of certain features, theorientation of the objects on window 232 or other suitablecharacteristics. The components of FIG. 3 may be adapted to output anindication of whether such characteristics are detected. Though, in someembodiments, a port, such as port 370 may be used to output an enlargedimage of all or a selected portion of the objects. The image may beoutput in digital form and magnified for display on a separate displaydevice.

FIG. 11 illustrates yet a further alternative embodiment of an assistivereading device using pinhole optics. As shown, the embodiment of FIG. 11includes an aperture plate 220 and imaging array 222. In the embodimentof FIG. 11, a solid state optical chamber 1110 is positioned between theillumination source and window 232 defining the imaging area. Opticalchamber 1110 acts as a light pipe to direct illumination from theillumination sources towards window 232.

As is known in the art, an optical chamber may be formed using solidstate elements that have surfaces defining the boundaries of the opticalchamber. The surfaces of the solid state elements are positionedrelative to the source of illumination and also relative to materials ofdifferent refractive index such that light emanating from theillumination source is reflected from those surfaces towards itsintended destination, here window 232. In the example of FIG. 11,optical chamber 1110 includes, for example, a surface 1112 positionedsuch that light from LED 1134 striking surface 1112 will be reflectedtowards window 232. Though, it is not a requirement that the surfaces ofoptical chamber 1110 directly reflect the light towards window 232. Forexample, light from LED 1134 may impinge on surface 1114 and bereflected to patterned reflector 260. From patterned reflector 260, thelight may be reflected to window 232. Accordingly, many configurationsof optical chamber 1110 are possible for providing suitable illuminationacross window 232.

FIG. 11 illustrates a further variation that is possible in someembodiments. FIG. 11 illustrates two light sources, LED 1134 and LED1136. In some embodiments, two light sources emitting light acrosssubstantially the same spectrum may be used. The two light sources maybe spatially separated to improve the uniformity of the illuminationacross the imaging area. For example, two LEDs that emit visible lightmay be used. In such an embodiment, both sources of illumination may beactivated simultaneously when an image is to be captured with imagingarray 222.

In other embodiments, multiple sources of illumination may be used, withdifferent sources emitting light in different spectra. For example, LED1134 and LED 1136 emit light in different spectra. LED 1134 may be avisible light source and LED 1136 may be an infrared light source. Thesesources of illumination may be operated at different times, such thatmultiple images of an object are captured, each formed based onillumination of a different spectra. In some embodiments, additionalinformation about an object under inspection may be obtained byprocessing multiple images.

As an example, certain characteristics of a bill of currency may be moreeasily detected in an image when the bill is illuminated with infraredlight than with visible light. In such a scenario, the denomination of abill of currency may be more accurately recognized by an image analysisalgorithm that computes a probability that the features that are morevisible when illuminated by infrared light appear in an image capturedby imaging array 222 while LED 1136 is illuminated. The imagingalgorithm may also compute the probability that features that are morevisible in visible light are present in an image captured by imagingarray 222 while LED 1134 is turned on. The analysis algorithm may thencompute a weighted probability indicating whether a bill of a specificdenomination is present in the imaging area by combining these twoprobabilities. However, any suitable algorithm may be used to controlmultiple sources of illumination such as LEDs 1134 and 1136 and toprocess images acquired when those light sources are turned on.

FIGS. 12A and 12B illustrate an alternative embodiment of a compactcurrency reader. In the embodiment illustrated, an optical system andprocessing components are packaged in a housing 1210 shaped to form akey fob 1200. The optical components may include pinhole imaging systemand a light source that illuminates an imaging area from the side, suchas in FIG. 6A, 8 or 9. Such components may be used to form a compactdevice, which has dimensions such as 30 mm by 25 mm by 10 mm. Buttons,such as buttons 1220A and 1120B may be incorporated at any suitablelocation on housing 1210. As with embodiments described above, buttons1220A and 1220B may serve as an input device for a user of the assistivereading device of FIG. 12A. One or more output devices (not shown) maybe incorporated within housing 1210. The output devices may include aspeaker and/or a mechanical vibrator to produce output in an audible ortactile form.

FIG. 12B illustrates that the assistive reader of FIG. 12A is sized toreceive only one corner or a bill 150. Though, other embodiments arepossible.

Turning to FIGS. 13A . . . 13E, a further embodiment is illustrated. Inthe embodiment of FIGS. 13A . . . 13E, an assistive device is attachedto a portable electronic device that includes an imaging array andprocessing components that can be programmed to perform functions of anassistive reading device. Such a portable electronic device may alsoinclude input and output devices though which commands to controloperation of the assistive reading device can be supplied by a user andoutput can be presented to the user.

As one example of a portable electronic device that may be used to forman assistive reading device, a cell phone 1300 is illustrated. As isknown in the art, a cell phone may include a camera that can captureimages. In FIG. 13A, lens 1302 of such a camera is illustrated. Cellphone 1300 may include input and output devices, such as buttons and aspeaker and/or mechanical vibrator. However, for simplicity, thosecomponents are not illustrated in FIG. 13A

FIG. 13B illustrates that an optical unit 1310 may be attached to cellphone 1300 to form an assistive reading device. Optical unit 1310 ispositioned on cell phone 1300 such that an object placed in an imagingarea of optical unit 1310 is projected through lens 1302 onto theimaging array of the camera within cell phone 1300. To facilitatepositioning of optical unit 1310, optical unit 1310 is formed with ahousing that includes attachment members, illustrated in FIG. 13B asattachment members 1316. Attachment members 1316 may have a fixed shapeadapted to conform to a housing of cell phone 1300. Alternatively,attachment members 1316 may have an adjustable shape that can beadjusted to conform to a housing of cell phone 1300, thereby securingoptical unit 1310 in position relative to camera 1302 (FIG. 13A).

The housing of optical unit 1310 has an upper portion 1312 and lowerportion 1314, separated to define a slot 1330 (FIG. 13C). As with theembodiment of an assistive reading device is FIGS. 12A and 12B, slot1330 is configured to receive a corner of a bill of currency for whichthe denomination is to be recognized. Lower portion 1314 may include oneor more illumination sources to illuminate an object to be imaged. Inaddition, lower portion 1314 may contain a support structure thatpositions a pinhole in an aperture plate such that the pinhole acts as alens focusing an image of an object placed in slot 1330 through lens1302 onto an imaging array 1322 within cell phone 1300. Such aconfiguration is illustrated in FIG. 13C, which represents a crosssection of the configuration in FIG. 13B taken along the line C-C.

As can be seen in FIG. 13C, an upper surface of lower portion 1314 isformed with a window 1332. An aperture plate 1340, in the embodimentillustrated, is placed parallel to window 1332.

FIG. 13D shows an enlarged version of the optical system illustratingfocusing provided by pinhole 1344 in aperture plate 1340. As can be seenin FIG. 13D, light reflected from an object placed into slot 1330 may befocused by pinhole 1344 onto lens 1302. Lens 1302 may then focus thatlight into an image on imaging array 1322. Components within cell phone1300 may capture that image from imaging array 1322 and process it usingtechniques as described above or in any other suitable way.

Light for forming such an image may be provided by a source ofillumination within optical unit 1310. For example, LEDs 1334A and 1334Bare illustrated (FIG. 13E). As in embodiments described above, multipleillumination sources may be used to provide uniform illumination acrosswindow 1332 or maybe used to allow images based on differentillumination spectra to be captured.

In some embodiments, it may be desirable to allow adjustment of theposition of aperture plate 1340 as a way to define the spacing betweenpinhole 1344 and lens 1302. Changing the spacing may adjust the focus ofoptical unit 1310. In the embodiment illustrated in FIGS. 13D and 13E,an adjustment mechanism is provided. By configuring aperture plate 1340in a generally circular shape, threads 1346 may be formed in anoutwardly directed ends of circular aperture plate 1340. Complimentarythreads 1348 may be formed on a member of lower portion 1314. As aresult of the threaded engagement between aperture plate 1340 and lowerportion 1314, rotation of aperture plate 1340 will cause aperture plate1340 to ride along the threads, thereby changing the separation betweenframe 1342, defining the lower surface of optical unit 1310 and apertureplate 1340

FIG. 13E illustrates an adjustment mechanism that may be used to used torotate aperture plate 1340 such that spacing between pinhole 1344 andlens 1302 is adjusted. In the embodiment of FIG. 13E, the adjustmentmechanism is a lever 1350 that extends outside the housing of opticalunit 1310. Lever 1350 is coupled to aperture plate 1340 such motion oflever 1350 causes rotation of circular aperture plate 1340. However, anysuitable mechanical or motorized mechanism may be used to alter theposition of aperture plate 1340.

Regardless of whether and what mechanism is used to focus an image of anobject on to an imaging array, the image may be captured from the arrayas a series of pixels, each representing an intensity value at a pointin the image. Those pixel values may then be processed to recognize thedenomination of a bill of currency or other symbol or object that may bepresent in the image. That processing may be performed in any suitableprocessing components, such as microprocessor 310 of FIG. 1 or amicroprocessor within a cell phone 1300 of FIG. 13A.

Regardless of the specific component that performs this processing, FIG.14 illustrates a process that may be used to identify a denomination ofa bill of currency.

FIG. 14 illustrates a method of operation of a processing system, suchas that illustrated in FIG. 3. The process of FIG. 14 begins at block1410 where the system is initialized. Initialization may occur inresponse to the device being powered on or other event, such as a userdepressing a button, such as button 120A or 120B. Regardless of thetriggering event, the system may be initialized in any suitable way.Initialization may be performed using techniques as known to thoseskilled in the art of digital circuit design. Such initialization mayinclude storing values in memory locations that are used duringcomputations that lead to identification of denomination of a bill ofcurrency.

Once the system is initialized, processing may proceed to block 1420where the system monitors for a button to be pressed by a user. When abutton press is detected, processing may proceed to decision block 1422.At decision block 1422, processing may branch depending on the contextof the button press detected at block 1420. In the embodimentillustrated in FIG. 1, an assistive reading device contains two buttons.In the process of FIG. 14, if both buttons are pressed simultaneously,the button press signals that the volume is to be adjusted. Accordingly,processing branches from decision block 1422 to block 1424. At block1424, the volume and/or mode of operation of the device is changed. Whenboth buttons are pressed simultaneously, each button press may signifythat the volume is to be decreased by one level. When the volume is atits lowest level, depressing both buttons may cause the device to switchoutput modes, providing outputs as vibratory pulses rather than audibletones.

In addition to changing the volume/mode, processing in response to abutton press at block 1424 may include other operations, such asoutputting a tone or other indication for a user that the button presswas detected, regardless of the specific processing performed at block1424. Once that processing is completed, the process loops back to block1420 and awaits further input. The process may continue in this loopuntil a command is received indicating another operation is to beperformed.

In the embodiment illustrated, other commands may be signaled by a userdepressing a single button. When a single button press is detected, theprocess will branch from block 1422 to block 1430. At block 1430, thesystem may be calibrated based on information captured periodicallywhile the system is not in use. In some embodiments, a surface of theupper edge 136 (FIG. 1) facing window 232 may have a calibrationpattern. Accordingly, when an image is captured while the system is notin use, the image may contain the calibration pattern. By comparing acalibration image to the calibration pattern, distortions introduced bythe optical system, imaging array or other components can be identified.Based on this comparison one or more calibration factors may becomputed. These calibration factors may include pixel by pixel gainadjustments, spatial transformations or other factors that can beapplied to an image to compensate for distortion.

In the embodiment illustrated, the calibration image is capturedperiodically to compensate for changes in the system over time. However,to save power, the calibration factors are not computed until an imageis to be captured. In other embodiments these functions may be performedat other times.

At block 1432, an image is captured. Processing at block 1432 mayinclude reading the output of an imaging array. Capturing an image atblock 1432 may also include applying the calibration factors computed toblock 1430.

Once the image is captured, the image may be processed to identifydenomination of the bill placed in the imaging area. An example ofprocessing that may be used to identify a denomination at block 1434 isprovided in conjunction with FIG. 15 below. Though, any suitableprocessing may be performed.

Regardless of the specific processing used to identify the denomination,once the denomination is identified, processing proceeds to block 1436where the denomination is announced. The mechanism of announcing thedenomination at block 1436 may depend on the mode set based onprocessing at block 1424. In scenarios in which the mode has been set atblock 1424 for an audible output, the denomination may be announced by aseries of tones. Though, in some embodiments, the denomination may beannounced using synthesized speech or other audible identification ofthe denomination. In embodiments in which the mode has been set for atactile output, the denomination may be announced as a series ofvibration pulses.

Regardless of how the denomination is announced, once the denominationhas been announced, processing may proceed to block 1438. At block 1438user preferences, such as the volume and mode of output determined atblock 1424 may be stored. Additionally, other data, such as thecalibration parameters determined at block 1430 may be stored. Thisinformation may be stored in non-volatile memory such that it will beretained when the system is powered off. Thereafter, the system may befully or partially powered off to conserve power until user input againindicating that a bill is to be read is received. If active componentsare used to monitor for a button press or to periodically “wake up” thesystem to capture a calibration image, those components may stay poweredon, for example, but all other components may be powered off.

FIG. 15 illustrates an exemplary process that may be performed toidentify a denomination of a bill of currency at block 1434. Thatprocessing begins at block 1510 where a portion of the captured imagecontaining a printed area of the bill is identified. Such anidentification may be made in any suitable way. An example of processingto identify the printed area is provided in conjunction with FIG. 16below.

Regardless of how the printed area is identified, processing proceeds toblock 1520 where the image contained within the printed area isrecognized. In embodiments in which the assisted reading device is acurrency reader, recognizing an image in the printed area involvesrecognizing the denomination of the bill.

In the embodiment illustrated, denomination of a bill is recognizedusing a fast normalized cross-correlation function (FNCC). The FNCCprocess involves comparing templates representing features ofdenominations of currency to the identified printed area of the bill ofcurrency. The denomination associated with the template that bestmatches the identified print area is selected as the denomination of thebill of currency.

In the FNCC process, a score is computed for each template, representinga degree of correlation between the template and the identified printedarea. These scores can then be compared to select the template that bestmatches the printed area. Alternatively or additionally, otherprocessing is possible based on the scores. For example, if the highestscore is below some threshold value, indicating a relatively poorcorrelation between the template and the image, the user may be signaledbecause a low score could indicate that the object in the imaging areais not a bill of currency or, due to an error or other factors, anaccurate image of the object was not acquired.

The templates representing denominations may be acquired in any suitablefashion. For example, the templates may be derived from images ofsamples of bills of currency of known denomination. Features of thebills that are useful in distinguishing between bills of differentdenominations may be recognized using manual or automated processing.The templates may be created by emphasizing the distinguishing features.

In some embodiments, the templates are represented as an array of pixelvalues. The template array may have fewer pixels than the identifiedprint area. In such embodiments, the FNCC process may entail acomparison of the template to multiple sub-regions of the identifiedprinted area to find the sub-region at which the template best matchesthe acquired image. The correlation between this sub-region and thetemplate is taken as the score for the template.

According to the FNCC process, the sub-region of the printed area bestmatching a template is identified in a two phase process. During thefirst phase, the template is sequentially compared to only a portion ofthe possible sub-regions throughout the identified print area. Fromthese sub-regions, the sub-region that best matches the template isselected. In the second phase, sub-regions surrounding this selectedsub-region are compared to the template.

As part of the comparison of the template to a sub-region, scoresrepresenting the correlation between the template and each of thesub-regions is computed. The highest score computed for any of thesub-regions during the second phase is selected as the overall score forthe comparison of the template to the identified print area. In thisway, the template is not compared to every possible sub-region of theidentified printed area. Because multiple templates are compared to theidentified print area in order to recognize the denomination of a billof currency, limiting the number of comparisons required can speedidentification of the denomination. Though, it should be appreciated anysuitable processing may be used to recognize a denomination.

Regardless of the manner in which the denomination is identified, atoken or other indication of the recognized denomination is returned atblock 1530. In the embodiment illustrated, the processing in FIG. 15 isimplemented as a sub-program called by the program implementing theprocessing of FIG. 14. Accordingly, the token, once returned, may beused for processing at block 1436 (FIG. 14) to announce the recognizeddenomination or for other reasons. Regardless of the manner in which therecognized denomination is used, the processing of FIG. 15 ends afterthe token identifying the denomination is generated.

Turning to FIG. 16, an example of a process to identify the portion ofan image representing a printed area is provided. In the embodimentillustrated, portions of an acquired image that depict borders on thebill of currency are first identified. Any portions of the image insidethe border are deemed to be printed areas of the bill of currency.Though any suitable method may be used to identify borders, ahistogramming approach may be used in some embodiments.

FIG. 16 illustrates an example of such a process. The process of FIG. 16begins at block 1610 where the portions of the image expected to containnon-printed borders are selected for processing. In embodimentsillustrated above, a bill of currency may be recognized from an image ofa corner of the bill and position sensors are used to control imageacquisition such that an image is acquired when the corner of the billis aligned in an imaging area. Accordingly, the acquired image can beexpected to contain sides of the bill of currency along two predefinedsides of the imaged area. The non-printed border can therefore beexpected to be adjacent to these sides. The pixels representing regionsadjacent these sides may be selected at block 1610 for processing.

The selected portions of the image may be filtered or otherwiseprocessed to highlight differences between non-printed border regionsand other portions of the image. For example, processing at block 1612may involve computing a Gaussian filter parameter, sigma, as is known inthe art. The computed parameter may be applied at block 1614 to performsmoothing of the portion of the image selected at block 1612 using aGaussian filter with the parameters determined at block 1612.

The smoothed image may be further processed. For example, processing maybe performed to enhance the appearance of edges of objects in the image.Accordingly, the exemplary process of FIG. 16 continues to block 1616where X and Y differential operators are applied. At block 1618,non-maximum suppression is performed using known techniques. Suchprocessing has the effect of de-emphasizing portions of the image thatare not indicative of edges of objects captured in the image. At block1620, a hysteresis threshold may be applied and an edge map may becreated at block 1622 using known processing techniques. The edge mapmay represent the portion of the image selected at block 1610 with edgesof objects emphasized.

Regardless of the preprocessing performed, a histogramming technique maybe applied to rapidly identify a boundary between the portions of thebill of currency to be identified. The histogramming process may beperformed twice, once along each side of the image such that bothborders may be identified. At block 1624 processing is performed alongone side and at block 1626 the same process is repeated along theperpendicular side. FIG. 17 provides an example of the histogrammingprocess that may be applied to detect the border along each side.

The process at FIG. 17 begins at block 1710 where an array of memorylocations representing a histogram is initialized. In this example, thearray is initialized with zero values. At block 1712, the histogramarray is filled with values derived from the edge map created at block1622 (FIG. 16). In this example, the array is filled with a value foreach row or column of pixels parallel to the side of the bill alongwhich a border region is to be detected. The value is derived bycounting the number of non-zero points in the edge map computed at block1622. Consequently, the histogram array populated at block 1712contains, in each successive entry, a count of the number of edge pixelsthat appear in the line parallel to the side of the bill along which thenon-printed border region is to be detected. Each successive value inthe array provides that count for a line one pixel width further awayfrom the side of the bill. If the line passes through the non-printedborder region, there should be few or no edges along that line and thecount in the histogram array should be near zero. Accordingly, thevalues in the histogram array may indicate the location relative to theside of the bill of currency of the transition between a non-printedborder area and the image area.

This processing begins at block 1714 where a detected flag is reset. Atblock 1716, processing of the histogram array begins, starting with thevalue representing the line closest to the side of the bill.

At decision block 1720, the process branches depending on whether allvalues in the array have been checked. If all entries have not beenchecked, processing branches to block 1722. Conversely, if all entrieshave been checked, processing branches to block 1736.

At block 1722 the histogram value at the next location in the array ischecked. If the edge detected flag is set, processing branches to block1736. Conversely, if the edge detected flag is not set, processingcontinues to decision block 1726.

At decision block 1726, the process branches depending on whether thehistogram value being checked is above a threshold value. If not, theprocess loops back to decision block 1720 and 1722 where the nextsubsequent value in the histogram array is processed.

Conversely, if, as a result of the comparison at decision block 1726, itis determined that the value in the histogram array exceeds thethreshold, processing proceeds to block 1728. If processing reachesblock 1728, the array value being processed may be tentatively assumedto define the transition between the non-printed border region and theprint area of the image. In subsequent processing steps, this assumptionmay be verified.

At block 1730, values from the initial image acquired of the bill ofcurrency are processed. Pixels at the location identified at block 1728,the presumptive boundary between the non-printed and printed areas ofthe bill, are selected for processing. An average intensity of pixels oneach side of the presumptive boundary between printed and non-printedareas are computed. Processing branches at decision block 1732 dependingon the magnitude of the difference between these intensity values. Ifthe intensity difference is greater than zero, processing branches toblock 1734 where the detected flag is set. Conversely, if the differenceis not greater than zero, processing loops back to decision block 1720,where the process may be repeated using a next value in the histogramarray.

Following setting of the detected flag at block 1734, processingproceeds to block 1736. Processing may also arrive at block 1736 onceall values in the histogram array have been checked, as determined atdecision block 1720.

Regardless of how processing reaches block 1736, an average pixelintensity value is computed for a long narrow strip of pixels within theregion presumed to be a portion of the non-printed border region basedon the location presumptively set at block 1728. In the exampleillustrated, the long narrow strip of pixels is 10 pixels long by twopixels wide. However, any suitable sized region may be used for thecalculation.

The process branches at decision block 1740, depending on the value ofthe average intensity computed at block 1736. If the average is lessthan a threshold, for example 150, the location determined at block 1728may be regarded as confirmed, and the processing of FIG. 17 may end witha value computed at block 1728 as the confirmed location of the boundarybetween the printed and non-printed areas of the bill of currency.Conversely, if the average is not less than the threshold applied atdecision block 1740, the process may continue to decision block 1742. Atdecision block 1742, the process may again branch. At decision block1742, the process branches, depending on the values of the pixels in thelong narrow region selected at block 1736. If the values of the pixelsover that region differ by more than a threshold, the process may branchto block 1744. If processing reaches block 1744, it may be assumed thatpixels falling within the non-printed border region identified at block1728 are actually within a printed area of the bill and the borderregion is set to zero. Setting a border region to zero may increase theamount of processing required at block 1520 (FIG. 15) when correlatingtemplates to the recognized printed area. However, it increases theaccuracy of the recognition performed at block 1520 by ensuring thatregions of the printed area are not unintentionally discarded byincorrectly labeling those regions as part of the non-printed borderarea.

Once the processing of block 1744 is completed, the process ofidentifying a non-printed border area may be completed. Similarly, if,as determined at decision block 1742, the pixel intensity difference isnot less than the threshold, the processing similarly ends. Ifprocessing ends following decision block 1742 because the pixelintensity difference is not less than the threshold, the edge of thenon-printed border region will be as determined at block 1728.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art.

As one example, output devices such as a speaker and a mechanicalvibrator are described. Other output devices may alternatively oradditionally be used and the device need not be integral with theassistive reading device. For example, a wireless connection may beprovided to a headset, such as a Bluetooth headset, may be included asan output device.

Such alterations, modifications, and improvements are intended to bepart of this disclosure, and are intended to be within the spirit andscope of the invention. Accordingly, the foregoing description anddrawings are by way of example only.

The above-described embodiments of the present invention can beimplemented in any of numerous ways. For example, the embodiments may beimplemented using hardware, software or a combination thereof. Whenimplemented in software, the software code can be executed on anysuitable processor or collection of processors, whether provided in asingle computer or distributed among multiple computers.

Further, it should be appreciated that a computer may be embodied in anyof a number of forms, such as a rack-mounted computer, a desktopcomputer, a laptop computer, or a tablet computer. Additionally, acomputer may be embedded in a device not generally regarded as acomputer but with suitable processing capabilities, including a PersonalDigital Assistant (PDA), a smart phone or any other suitable portable orfixed electronic device.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audible format.

Such computers may be interconnected by one or more networks in anysuitable form, including as a local area network or a wide area network,such as an enterprise network or the Internet. Such networks may bebased on any suitable technology and may operate according to anysuitable protocol and may include wireless networks, wired networks orfiber optic networks.

Also, the various methods or processes outlined herein may be coded assoftware that is executable on one or more processors that employ anyone of a variety of operating systems or platforms. Additionally, suchsoftware may be written using any of a number of suitable programminglanguages and/or programming or scripting tools, and also may becompiled as executable machine language code or intermediate code thatis executed on a framework or virtual machine.

In this respect, the invention may be embodied as a computer readablemedium (or multiple computer readable media) (e.g., a computer memory,one or more floppy discs, compact discs, optical discs, magnetic tapes,flash memories, circuit configurations in Field Programmable Gate Arraysor other semiconductor devices, or other tangible computer storagemedium) encoded with one or more programs that, when executed on one ormore computers or other processors, perform methods that implement thevarious embodiments of the invention discussed above. The computerreadable medium or media can be transportable, such that the program orprograms stored thereon can be loaded onto one or more differentcomputers or other processors to implement various aspects of thepresent invention as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that can be employed to program a computer or otherprocessor to implement various aspects of the present invention asdiscussed above. Additionally, it should be appreciated that accordingto one aspect of this embodiment, one or more computer programs thatwhen executed perform methods of the present invention need not resideon a single computer or processor, but may be distributed in a modularfashion amongst a number of different computers or processors toimplement various aspects of the present invention.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconveys relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

Various aspects of the present invention may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in its application to the details and arrangement of componentsset forth in the foregoing description or illustrated in the drawings.For example, aspects described in one embodiment may be combined in anymanner with aspects described in other embodiments.

Also, the invention may be embodied as a method, of which an example hasbeen provided. The acts performed as part of the method may be orderedin any suitable way. Accordingly, embodiments may be constructed inwhich acts are performed in an order different than illustrated, whichmay include performing some acts simultaneously, even though shown assequential acts in illustrative embodiments.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

What is claimed is:
 1. Compact apparatus for close-range imaging of anobject in an imaging area, the apparatus comprising: a support structuredefining the imaging area; a surface supported by the support structure,the surface having a pin-hole aperture therethrough; an imaging arraysupported by the support structure, wherein: the surface is positionedwith the pin-hole aperture disposed in an optical path between theimaging area and the imaging array; the imaging array is spaced from theimaging area by a distance of less than 25 mm; and at least 75 mm² ofthe imaging area is focused on the imaging array through the pin-holeaperture.
 2. The compact apparatus of claim 1, wherein the pin-holeaperture provides a field of view of at least 75 degrees.
 3. The compactapparatus of claim 1 adapted as a currency reader, wherein: the supportstructure comprises a slot sized and positioned to provide a passage fora bill of currency between the imaging area and an area external to thecompact apparatus.
 4. The compact apparatus of claim 3, wherein: thesupport structure comprises at least one alignment feature sized andpositioned to align a corner of the bill in the imaging area; and thecompact apparatus further comprises circuitry adapted to process animage of the corner of the bill to identify a unique patternrepresenting a denomination of the bill.
 5. The compact apparatus ofclaim 4, wherein: the slot is sized and positioned to receive only acorner of the bill.
 6. The compact apparatus of claim 5, wherein thesupport structure comprises a housing, the housing being shaped as a keyfob.
 7. The compact apparatus of claim 4, wherein: the compact apparatusfurther comprises a speaker; and the circuitry comprises an audiogenerator coupled to the speaker, the audio output generator adapted togenerate an audio signal representative of an identified denomination ofthe bill.
 8. The compact apparatus of claim 7, wherein: the compactapparatus further comprises a user control mechanism, the user controlmechanism consisting essentially of two buttons; the circuitry isadapted to respond to a user activating one of the two buttons byprocessing an image to identify a number representing a denomination ofthe bill; and the circuitry is adapted to respond to a user activatingtwo of the two buttons by altering a volume at which the audio outputsignal is rendered through the speaker.
 9. The compact apparatus ofclaim 8, wherein: the compact apparatus comprises a housing comprising awider surface and two opposing side surfaces perpendicular to the widersurface, each side surface being narrower than the wider surface in atleast one dimension; the slot passes through the wider surface; and oneof the two buttons is disposed in each of the narrower surfaces.
 10. Thecompact apparatus of claim 4, wherein the circuitry comprises aprocessor and a computer storage medium encoded with computer executableinstructions that, when executed by the processor, process the image ofthe corner of the bill to identify the number representing thedenomination of the bill.
 11. The compact apparatus of claim 10, whereinthe image of the corner of the bill comprises an image of an area withdimensions less than 15 mm by 20 mm.
 12. The compact apparatus of claim4, wherein: the compact apparatus further comprises at least two opticalposition sensors, each optical position sensor adapted to generate acontrol signal indicating position of the bill within the slot; and thecircuitry is adapted to process an image automatically in response tothe control signals from the at least two optical position sensors. 13.The compact apparatus of claim 1, wherein: the optical path between theimaging area and the imaging array is free of mirrors.
 14. The compactapparatus of claim 1, further comprising: a light source; an opticalelement disposed between the light source and the imaging area, theoptical element refracting light from the light source by at least 45degrees, whereby light from the light source is directed at the imagingarea.
 15. The compact apparatus of claim 1, further comprising: a prismfilm adjacent the imaging area; a light source, the light source beingpositioned: between the surface and the prism film so as to irradiatethe prism film; and outside of any direct optical path between theimaging array and the imaging area.
 16. The compact apparatus of claim1, further comprising a light source, the light source being positioned:between the surface and the imaging area; and offset from a line betweena center of the image array and a center of the imaging area in adirection perpendicular to the line.
 17. The compact apparatus of claim16, further comprising: a reflector comprising a reflective surface, thereflector being positioned offset from the line in a directionperpendicular to the line with the reflective surface facing the lightsource.
 18. The compact apparatus of claim 17, wherein the reflectorcomprises a patterned reflector, the reflector comprising a pattern thatis more reflective in a center of the reflective surface than along atleast two edges of the reflective surface.
 19. The compact apparatus ofclaim 16, wherein the light source comprises a first light emittingelement and a second light emitting element, the first light emittingelement and the second light emitting element emitting light atdifferent wavelengths.
 20. The compact apparatus of claim 16, whereinthe first light emitting element emits light in a visible spectrum andthe second light emitting element emits light in an infrared (IR)spectrum.
 21. The compact apparatus of claim 20, further comprising:circuitry coupled to the imaging array adapted to identify adenomination of a bill disposed within the imaging area, the circuitryadapted to identify the denomination by processing a first image outputfrom the imaging array while the imaging area is illuminated with onlythe first light source and a second image output from the imaging arraywhile the imaging area is illuminated with only the second light source.22. The compact apparatus of claim 1, further comprising: a solid lightpipe oriented to distribute light to the imaging area.
 23. The compactapparatus of claim 1, wherein: the imaging area comprises a planarregion; a region of the surface comprising the pin hole is planar; and anormal to the planar region of the imaging area is parallel to a normalto the planar region of the surface.
 24. The compact apparatus of claim1, wherein: the imaging area comprises a planar region; a region of thesurface comprising the pin hole is planar; and a normal to the planarregion of the imaging area is transverse to a normal to the planarregion of the surface.
 25. The compact apparatus of claim 24, whereinthe imaging array is planar and transverse to the planar region of thesurface.
 26. The compact apparatus of claim 1, wherein the supportstructure comprises a mechanism for mechanically coupling the compactapparatus to an electronic device with a display screen.
 27. The compactapparatus of claim 26, wherein: the compact apparatus further comprisesa speaker; and the circuitry comprises a text to speech convertercoupled to the speaker, the text to speech converter adapted to generatean audio signal representative of text on the display screen of theelectronic device.
 28. Compact apparatus for close-range imaging of anobject, the apparatus comprising: a housing having dimensions of lessthan 100 mm in length, 20 mm in height and 50 mm in width; a planarimaging area mechanically coupled to the housing; an imaging arraymechanically coupled to the housing; a planar surface mechanicallycoupled to the housing, the planar surface having a pin hole aperturetherethrough, and the planar surface being positioned in an optical pathbetween the imaging area and the imaging array.
 29. The compactapparatus of claim 28, wherein the housing comprises a slot shaped andpositioned to guide a corner of a bill of currency into the imagingarea.
 30. The compact apparatus of claim 29, further comprising:circuitry, coupled to the imaging array, adapted to process an output ofthe imaging array and recognize a denomination of a bill having a cornerin the imaging area; and an audio output mechanism coupled to thecircuitry, the audio output mechanism adapted to output an audibleindication of the recognized denomination of the bill.
 31. The compactapparatus of claim 30, wherein: the housing comprises a first surfacespanning the length and width of the housing, the first surfacecomprising a textured gripping area, and wherein the slot passes throughthe first surface; the housing comprises a first end surface and asecond end surface, each joined to the first surface at an edge and eachspanning with width and height of the housing; and the compact apparatusfurther comprises a first control button disposed in the first endsurface and a second control button in the second end surface.